Interacting with Networks and Databases - Beginning Java 7 - page 818

byaportnumber). Clients wanting toreceive those datagram packets create amul-
ticastsocketthatusesthatportnumber.Theyrequesttojointhegroupthrougha join
group operation thatspecifiesthespecialIPaddress.Atthispoint,theclientcanre-
ceivedatagrampacketssenttothegroup,andcanevensenddatagrampacketstooth-
ergroupmembers.Aftertheclienthasreadalldatagrampacketsthatitwantstoread,
it removes itself from the group by applying a leave group operation that specifies
the special IP address.
IPv4addresses224.0.0.1to239.255.255.255(inclusive)arereservedforuseasmul-
ticast group addresses.

Listing 9-6 presents a multicasting server.

Listing 9-6. Multicasting datagram packets

import java.io.IOException;

import java.net.DatagramPacket;
import java.net.InetAddress;
import java.net.MulticastSocket;

class MCServer
{

final static int PORT = 10000;
public static void main(String[] args)
{

try (MulticastSocket mcs = new MulticastSocket())
{

InetAddress group = InetAd-

dress.getByName("231.0.0.1");
byte[] dummy = new byte[0];
DatagramPacket dgp = new DatagramPacket(dummy, 0,
group, PORT);
int i = 0;
while (true)
{

byte[] buffer = ("line "+i).getBytes();
dgp.setData(buffer);